This invention relates to a novel design of secondary isolating contacts in circuit breakers. This invention is aimed at achieving high modularity so that various accessories provided in the circuit breaker can be easily added and/or replaced.
Circuit breakers for low voltage generally find application in the current range of upto 6400A. These circuit breakers are available in Fixed and Drawout versions. Drawout version facilitates easy maintenance and installation.
For drawout circuit breaker, a chamber like unit often called as Cradle is generally additionally required, through which current carrying parts of the circuit breaker get connected in sliding and/or plug-in way. Power circuit, which handles current as per the ampere rating of circuit breaker ( less than =6400 Amp), has one arrangement, while various accessories viz. Closing release, shunt release, electrical charging device, auxiliary switch etc. which form part of control circuit have an independent arrangement. The current of control circuits is of the order of 10 Amperes.
The arrangement of control circuit has to be suitable for as many accessories as are present in modem day circuit breakers. The number varies from about twenties to about sixties.
Drawout circuit breaker can assume three different situations:
1. xe2x80x9cServicexe2x80x9d position; where Power as well as control circuit is connected. This is the position when circuit breaker is in operation.
2. xe2x80x9cTestxe2x80x9d position; where Power circuit is disconnected but control circuit is connected. In this position, the circuit breaker can be tested for proper functioning without switching and/or carrying power.
3. xe2x80x9cIsolatedxe2x80x9d position; when control circuit is also disconnected.
Electrical micro switches are generally mounted in the cradle which sense the position of circuit breaker in cradle.
The arrangement for control circuit is required in line with the accessories chosen by different users and hence needs to be independently modular.
Many a time, because of process interlocking requirements, few control circuits need to be connected only in service and/or test position.
Presently available designs generally meet only basic requirement of circuit breaker, but these designs do not meet the modularity and circuit breaker position sensing and process interlocking needs.
Our design system effectively meets all these requirements in unique way.
Our design system of the present invention of contacts for connected of control circuit is called secondary isolating contacts (abbreviated as SICs). The basic module consists of the minimum possible i.e. ONE. Hence as less as one SIC can be provided in our circuit breaker. This design is thus called a unipolar design.
One SIC consists of one breaker SIC and one cradle SIC. The breaker SIC slides over the cradle SIC thus providing the desired connection.
In circuit breaker, many accessories are added by the user at a later date. In our design, when such an accessory is added, the corresponding SIC(s) can be added without disturbing the previously present SIC(s).
Similarly, when any accessory needs replacement, the corresponding breaker SIC(s) can be withdrawn without disturbing other SICs.
The cradle SICs design is such that it provides contact in Service+Test+Isolated position or any one position or combination of any two or all three positions, as desired.